The invention relates to a formulation and method of using same for improving well productivity and oil recovery factor in hydrocarbon reservoirs and improving the transportation of said oil through pipelines from downhole to potentially very long distances from the natural source to processing units such as refineries, oil improvement units or dehydrating and/or diluting treatment sites for improving quality and flowability of natural heavy and extra heavy oil, and use of the formulation in an integral exploitation method to improve cold production recovery factor and transport of heavy and extra heavy oil.
Improvement of reservoir recovery factor and flowability in tubing and pipelines of very viscous heavy oil, and improvement of well productivity of heavy and extra heavy oil reservoir wells such as those found in the Orinoco River Belt in the Bolivarian Venezuelan Republic, is clearly desirable. Increase of the recovery factor in cold exploitation of such reservoirs and easy transportation of such resources through existing infrastructure and low cost means of cold transportation through long distances is a real need. Some of the largest reservoirs of heavy and extra heavy oil in the world are in Venezuela and hold oil having API gravity within the range of 6 to 16. Unfortunately, recovery factors of such reservoirs, and well production rate of much of this oil is unacceptable, and the possibilities of transporting the produced viscous oil by pipeline for long distances away from the well site are disappointing.
It is a high concern in the exploitation of heavy and extra heavy oil reservoirs to increase the final oil-in-place recovery during the reservoir lifetime, and also to increase productivity of the wells and lower the surface transportation cost to improve the overall economic value of the exploitation. Centralization of the wells or pad of wells production in a high capacity production processing unit where oil treatment can be achieved on a greater scale for demulsification, dehydration, desalting, or further processing; such as the refining of said oil or upgrading treatment in an oil process unit for improving the flowability and sour characteristics of the oil for further processing or refining is desirable.
To satisfy these needs, primary cold production schemes are quickly abandoned in favor of thermal methods to improve well flowability by reducing oil viscosity in the reservoirs, high output pumping systems are used to output the oil to the surface, and a combination of dilution and pumping through surface pipelines make it possible to transport heavy and extra heavy oil to production units. These processes, however, are very costly. The wells still remain with very low productivity, and reservoirs still have a very low output in terms of final oil recovery. More than 90% of the original oil in place is left behind in the reservoir. In addition, extremely serious problems of sour gas production such as H2S and CO2 are being reported and increase with steam injection in the several pilot thermal production methods evaluated. This sour gas production in a mass scale is a threat to life in or near to populated areas, requires high security standards for workers in the facilities, further these processes are limited by the availability in amount and cost of current downhole or surface sour gas mitigation abilities. Thermal recovery methods, lifting and surface transportation methods typically produce final oil recovery below 15%.
Venezuelan heavy and extra heavy Orinoco River Belt oil sandstones are exceptional reservoirs. 60% of the reservoirs of this type have a KH/U value between 40 and close to 1,000 in very many cases. Unlike other reservoirs, however, the oil in Venezuelan extra heavy oil reservoirs is flowable at reservoir conditions.
Even these wells, however, have a final recovery by cold production which is very low and perhaps in most cases below three (3) percent of the original oil in place. The conditions for flow of oil in those reservoirs, with even excellent petrophysical properties, are very unfavorable to the flow of oil. The components of the heavy and extra heavy oil, particularly the asphaltenes in natural form in the native oil, are capable by natural fluid-rock interactions of generating an oil-wet condition at the surface of the natural mineral components of the sandstone. This produces the most adverse conditions to flow of oil in a porous media. This is a natural oil-wet condition of the reservoir media, which is a completely different condition as compared to formation damage in the well resulting from drilling or production activities, which could also happen in the well. The viscosity of the oil changes dramatically with the change in temperature and therefore there is greater drag pressure in the flow during lifting of the oil through the tubing and flowing in pipelines at surface conditions. To improve flow in the pipelines of the natural oil, known efforts include diluting with naphtha, gasoil, and diluents of light oil, but this is costly and the use of such diluents is not practical in high mass production scenarios such as the Orinoco River Belt well production area.
The need still exists to increase final oil-in-place recovery during the reservoir lifetime, to increase the productivity of wells and to reduce surface transportation cost to improve the overall economic value of the exploitation in an easy, environmentally safe and highly economic return of investment in cold production exploitation schemes of heavy and extra heavy oil reservoirs.